U.S. patent number 7,064,346 [Application Number 10/765,901] was granted by the patent office on 2006-06-20 for transistor and semiconductor device.
This patent grant is currently assigned to Japan Science and Technology Agency. Invention is credited to Masashi Kawasaki, Hideo Ohno.
United States Patent |
7,064,346 |
Kawasaki , et al. |
June 20, 2006 |
**Please see images for:
( Certificate of Correction ) ** |
Transistor and semiconductor device
Abstract
In an npn-type transistor, the emitter 42 and the collector 43
are formed of an n-type transparent semiconductor, and the base 41
is formed by a p-type transparent semiconductor. The base electrode
44, the emitter electrode 45 and the collector electrode 46 are
formed respectively on the base 41, the emitter 42 and the
collector 43. As the n-type transparent semiconductor, for example,
n-type ZnO is used. The n-type ZnO is ZnO doped with, for example,
group III elements, group VII elements. As the p-type transparent
semiconductor, for example, p-type ZnO is used. The p-type ZnO is
ZnO doped with, for example, group I elements and group V
elements.
Inventors: |
Kawasaki; Masashi (Sagamihara,
JP), Ohno; Hideo (Sendai, JP) |
Assignee: |
Japan Science and Technology
Agency (Saitama, JP)
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Family
ID: |
18192883 |
Appl.
No.: |
10/765,901 |
Filed: |
January 29, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050127380 A1 |
Jun 16, 2005 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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09850732 |
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6727522 |
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PCT/JP99/06300 |
Nov 11, 1999 |
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Foreign Application Priority Data
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Nov 17, 1998 [JP] |
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10-326889 |
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Current U.S.
Class: |
257/43; 257/613;
257/197; 257/E29.099; 257/E29.094; 257/614; 257/192; 257/E29.255;
257/E29.182; 257/E27.12 |
Current CPC
Class: |
H01L
29/4908 (20130101); H01L 29/7317 (20130101); H01L
29/78 (20130101); H01L 27/15 (20130101); H01S
5/0261 (20130101); H01L 29/78618 (20130101); H01L
29/22 (20130101); H01L 29/7869 (20130101); H01L
29/45 (20130101); H01L 29/517 (20130101); H01L
33/28 (20130101) |
Current International
Class: |
H01L
29/10 (20060101) |
Field of
Search: |
;257/43,613,E29.079,E29.094,E29.099,E29.296,E21.698,E21.699 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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56-125868 |
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Oct 1981 |
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JP |
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57-132191 |
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Aug 1982 |
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JP |
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63-121886 |
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May 1988 |
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JP |
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01-065868 |
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Mar 1989 |
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JP |
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07-114351 |
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May 1995 |
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JP |
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9-199732 |
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Jul 1997 |
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JP |
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Other References
AOnodera, et al., "Ferroelctric Properties in Piezoelectric
Semiconductor Zn1 -xMxO (M=Li, Mg)", Jpn. J. Appl. Phys., vol. 36,
Part 1, No. 9B, pp. 6008-6011, Sep. 1997. cited by other .
A.Onodera, et al., "Dielectric Activity and Ferroelectricity in
Piezoelectric Semiconductor Li-DoppedZnO", Jpn. J. Appl. Phys.,
vol. 35, Part 1, No. 9B, pp. 65160-65162, Sep. 1996. cited by other
.
Boesen, et al., "ZnO Field-Effect Transistor", Proceedings of the
IEEE, pp. 2094-2095, Nov. 1968. cited by other.
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Primary Examiner: Parker; Kenneth
Assistant Examiner: Diz; Jose R.
Attorney, Agent or Firm: Niefeld IP Law, PC
Parent Case Text
This application is a divisional of U.S. patent application Ser.
No. 09/850,732, filed Jun. 6, 2001, now U.S. Pat. No. 6,727,522,
which is a U.S. national stage application of international
application PCT/JP99/06300 filed Nov. 11, 1999, which claims the
benefit of Japanese application 10-326889, filed Nov. 17, 1998.
The disclosure of application Ser. No. 09/850,732 is incorporated
herewith by reference.
Claims
What is claimed is:
1. A transistor, comprising: an emitter, a collector and a base
selected from the group consisting of: (a) an emitter and a
collector made of a transparent n-type semiconductor, and a base
made of a transparent p-type semi conductor, and (b) a base made of
a transparent n-type semiconductor, and an emitter and a collector
made of a transparent p-type semiconductor, said n-type
semiconductor comprising any one of zinc oxide ZnO, zinc magnesium
oxide Mg.sub.xZn.sub.1-x O, zinc cadmium oxide Cd.sub.x Zn.sub.1-x
O and cadmium oxide CdO, doped with group III elements or group VII
elements, and said transparent p-type semiconductor comprising any
one of zinc oxide ZnO, zinc magnesium oxide Mg.sub.x Zn.sub.1-x O,
zinc cadmium oxide Cd.sub.x Zn.sub.1-x O and cadmium oxide CdO,
doped with group I elements or group V elements; and a base
electrode, an emitter electrode and a collector electrode, in which
(1) a transparent conductive material doped or undoped with any one
of group III elements, group VII elements and group I elements, (2)
a transparent conductor, or (3) an untransparent electrode material
are used partially or entirely, the base electrode, the emitter
electrode and the collector electrode being respectively formed on
said base, said emitter and said collector.
2. A semiconductor device, comprising: the transistor according to
claim 1; and a light emission portion formed of a region continuous
to said collector or said emitter of said transistor or a region of
another semiconductor connected to said collector or said emitter,
and a semiconductor layer joined to said region.
3. A semiconductor device, comprising: the transistor according to
claim 1, and a capacitor formed of a region continuous to said
collector and said emitter of said transistor or a region of
another semiconductor or a conductor connected to said collector or
said emitter, an insulating layer on said region, and a
semiconductor layer or a conductive layer on said insulating
layer.
4. A semiconductor device, wherein a plurality of the semiconductor
devices according to claim 3 are arranged in a matrix shape, and a
capacitor or a light emission portion is driven by each
transistor.
5. A semiconductor device, comprising a plurality of transistors
according to claim 1, and an insulating layer, said insulating
layer is between transistors of said plurality of transistors;
wherein said insulating layer comprises a transparent insulating
material including at least one of insulative ZnO doped with
elements capable of taking a valence of one as a valence number or
group V elements, a transparent insulating oxide, and a transparent
insulator.
6. A semiconductor device, comprising: a plurality of transistors
according to claim 1; and wiring between said plurality of
transistors, wherein said wiring comprises a transparent conductive
material including at least one of conductive ZnO doped or undoped
with group III elements, group VII elements, group I elements and
group V elements, a transparent conductor comprising at least one
of In.sub.2 O.sub.3, SnO.sub.2 and , (In--Sn)O.sub.x, or a
un-transparent electrode material.
7. A semiconductor device, comprising: the transistor according to
claim 1; and an inductor comprising a transparent conductive
material, said transparent conductive material comprising at least
one of conductive ZnO doped or undoped with group III elements,
group VII elements, group I elements and group V elements, and a
transparent conductor comprising at least one of
In.sub.2O.sub.3,SnO.sub.2 and (In--Sn)O.sub.x.
8. A semiconductor device, wherein a plurality of the semiconductor
devices according to claim 2 are arranged in a matrix shape, and a
capacitor or a light emission portion is driven by each
transistor.
9. The transistor of claim 1, wherein said transparent n-type
semiconductor includes at least conductive ZnO doped with group III
elements or group VII elements.
10. The transistor of claim 1, wherein said transparent p-type
semiconductor includes at least conductive ZnO doped with group I
elements or group V elements.
11. The transistor of claim 1, wherein said transparent conductive
material includes at least one conductive ZnO undoped and
conductive ZnO doped with at least one of group III elements, group
VII elements, and group I elements.
12. The transistor of claim 1, wherein said transparent conductive
material includes at least one of In.sub.2O.sub.3, SnO.sub.2 and
(In--Sn)O.sub.x.
13. The transistor of claim 1, wherein said base is made of a
transparent n-type semi conductor.
14. The transistor of claim 1, wherein said base is made of a
transparent p-type semi conductor.
15. A method of making a transistor, comprising: depositing an
emitter, a collector, and a base, wherein said emitter, said
collector and said base are selected from the group consisting of:
(a) an emitter and a collector made of a transparent n-type
semiconductor, and a base made of a transparent p-type
semiconductor, and (b) a base made of a transparent n-type
semiconductor, and an emitter and a collector made of a transparent
p-type semiconductor, said n-type semiconductor comprising any one
of ZnO, zinc magnesium oxide Mg.sub.x Zn.sub.1-xO, zinc cadmium
oxide Cd.sub.xZn.sub.1-xO, and cadmium oxide CdO, and said n-type
semiconductor is doped with group III elements or group VII
elements; depositing a base, an emitter and a collector, wherein
said base, or said emitter and said collector are made of a
transparent p-type semiconductor comprising at least one of ZnO,
zinc magnesium oxide Mg.sub.xZn.sub.1-xO, zinc cadmium oxide
Cd.sub.xZn.sub.1-xO, and cadmium oxide CdO, said p-type
semiconductor doped with group I elements or group V elements; and
depositing a base electrode, an emitter electrode and a collector
electrode, wherein said base electrode, said emitter electrode and
said collector electrode comprise a transparent conductive material
comprising conductive ZnO doped or undoped with any one of group
III elements, group VII elements and group I elements, or a
transparent conductive material comprising at least one of
In.sub.2O.sub.3, SnO.sub.2 and (In--Sn)O.sub.x,or an untransparent
electrode material and wherein said base electrode, said emitter
electrode and said collector electrode are respectively formed on
said base, said emitter, and said collector.
16. The method of claim 15, wherein said transparent n-type
semiconductor includes at least conductive ZnO doped with group III
elements or group VII elements.
17. The method of claim 15, wherein said transparent p-type
semiconductor includes at least conductive ZnO doped with group I
elements or group V elements.
18. The method of claim 15, wherein said transparent conductive
material includes at least one of conductive ZnO undoped and
conductive ZnO doped with any one of group III elements, group VII
elements and group I elements.
19. The method of claim 15, wherein said transparent conductive
material includes at least one of In.sub.2O.sub.3, SnO.sub.2 and
(In--Sn)O.sub.x.
20. The method of claim 15, wherein said base is made of a
transparent n-type semiconductor.
21. The method of claim 15, wherein said base is made of a
transparent p-type semiconductor.
22. A method of making a transistor, comprising: providing an
emitter and a collector, or a base, wherein said emitter, said
collector and said base are selected from the group consisting of:
(a) an emitter and a collector made of a transparent n-type
semiconductor, and a base made of a transparent p-type
semiconductor, and (b) a base made of a transparent n-type
semiconductor, and an emitter and a collector made of a transparent
p-type semiconductor, said n-type semiconductor comprising at least
one of ZnO, zinc magnesium oxide Mg.sub.xZn.sub.1-xO, zinc cadmium
oxide Cd.sub.xZn.sub.1-xO, and cadmium oxide CdO, and said n-type
semiconductor is doped with at least one of group III elements and
group VII elements; providing a base, or an emitter and a
collector, wherein said base, or said emitter and said collector
are made of a transparent p-type semiconductor comprising at least
one of zinc oxide ZnO, zinc magnesium oxide Mg.sub.xZn.sub.1-xO,
zinc cadmium oxide Cd.sub.xZn.sub.1-xO, and cadmium oxide CdO, and
said p-type semiconductor is doped at least one of with group I
elements and group V elements; and providing a base electrode, an
emitter electrode, and a collector electrode; wherein said base
electrode, said emitter electrode, and said collector electrode
respectively are formed on said base, said emitter, and said
collector; wherein said base electrode, said emitter electrode, and
said collector electrode comprise: (1) a transparent conductive
material comprising conductive ZnO that is undoped and conductive
ZnO that is doped with at least one of group III elements, group
VII elements, and group I elements; or (2) a transparent conductor
comprising at least one of In.sub.2O.sub.3, SnO.sub.2and
(In--Sn)O.sub.x; or (3) an un-transparent electrode material.
23. A method of using a transistor, said transistor comprising: an
emitter and a collector, or a base, wherein said emitter, said
collector and said base are selected from the group consisting of:
(a) an emitter and a collector made of a transparent n-type
semiconductor, and a base made of a transparent p-type
semiconductor, and (b) a base made of a transparent n-type
semiconductor, and an emitter and a collector made of a transparent
p-type semiconductor, said n-type semiconductor comprising any one
of zinc oxide ZnO, zinc magnesium oxide Mg.sub.xZn.sub.1-xO, zinc
cadmium oxide Cd.sub.xZn.sub.1-xO, and cadmium oxide CdO, and said
n-type semiconductor is doped with at least one of group III
elements and group VII elements; or a base, or an emitter and a
collector, wherein said base, or said emitter and said collector
are made of a transparent p-type semiconductor comprising any one
of zinc oxide ZnO, zinc magnesium oxide Mg.sub.xZn.sub.1-xO, zinc
cadmium oxide Cd.sub.xZn.sub.1-xO, and cadmium oxide CdO, and said
p-type semiconductor is doped with at least one of group I elements
and group V elements; a base electrode, an emitter electrode, and a
collector electrode; wherein said base electrode, said emitter
electrode, and the collector electrode are respectively formed on
said base, said emitter, and said collector; wherein said base
electrode, said emitter electrode, and said collector electrode
comprise: (1) a transparent conductive material comprising one of
conductive ZnO that is undoped and conductive ZnO that is doped
with at least one of group III elements, group VII elements, and
group I elements; or (2) a transparent conductor comprising at
least one of In.sub.2O.sub.3, SnO.sub.2 and (In--Sn)O.sub.x,or (3)
an un-transparent electrode material; and said method comprising
applying a voltage across at least one electrode of said
transistor.
24. A transistor, comprising: an emitter, a collector and a base
made of a transparent n-type semiconductor selected from the group
consisting of: (a) an emitter and a collector made of a transparent
n-type semiconductor, and a base made of a transparent p-type
semiconductor, and (b) a base made of a transparent n-type
semiconductor, and an emitter and a collector made of a transparent
p-type semiconductor, said transparent n-type semiconductor
comprising at least one of zinc oxide ZnO, zinc magnesium oxide
Mg.sub.xZn.sub.1-xO, zinc cadmium oxide Cd.sub.xZn.sub.1-xO, and
cadmium oxide CdO, and said transparent n-type semiconductor is
doped with at least one of group III elements and group VII
elements; a base, or an emitter and a collector made of a
transparent p-type semiconductor, said transparent p-type
semiconductor comprising any one of zinc oxide ZnO, zinc magnesium
oxide Mg.sub.xZn.sub.1-xO, zinc cadmium oxide Cd.sub.xZn.sub.1-xO,
and cadmium oxide CdO, and said transparent p-type semiconductor is
doped with at least one of group I elements and group V elements;
and a base electrode, an emitter electrode, and a collector
electrode; wherein said base electrode, said emitter electrode, and
said collector electrode are respectively formed on said base, said
emitter, and said collector; and wherein said base electrode, said
emitter electrode, and said collector electrode comprise: (1) a
transparent conductive material comprising one of conductive ZnO
that is un-doped and conductive ZnO that is doped with at least one
of group III elements, group VII elements, and group I elements; or
(2) a transparent conductor comprising at least one of
In.sub.2O.sub.3, SnO.sub.2, and (In--Sn)O.sub.x, or (3) an
un-transparent electrode material.
Description
FIELD OF THE INVENTION
The present invention relates to a transistor and a semiconductor
device, more particularly to a transparent transistor, a
semiconductor device having the transparent transistor stacked
thereon, and a semiconductor device to which the transparent
transistor is applied for driving a light emission device, for
reading/writing data from/to a memory, and for other purposes. It
should be noted that in the present invention, a concept of
"transparent" includes a concept of "being transparent or offering
light transmission property" for the sake of simplifying
descriptions.
DESCRIPTIONS OF THE RELATED ARTS
A thin film transistor using amorphous silicon, polycrystalline
silicon or the like has been generally used as a transistor for use
in driving liquid crystal display devices. Since these materials
exhibit photosensitivity for the visible light region, carriers are
generated by a beam of light, and resistivity of a thin film
constituting the thin film transistor is lowered. For this reason,
when the beam of light is radiated thereonto, the transistor may be
made to be a turn-on state, in spite of the fact that the
transistor must be controlled to be a turn-off state. Accordingly,
to keep the transistor at the turn-on state, the lowering of the
carrier resistivity of the thin film due to the radiation of the
beam of light has been heretofore prevented by the use of a light
shielding layer made of a metal film or the like.
DISCLOSURE OF THE INVENTION
Generally, the liquid crystal display device has been widely used
for a notebook type personal computer or the like, and an
energy-saving measure, a high luminance and a miniaturization have
been requested of the liquid crystal display device. To reply to
these requests, it is effective to increase a rate of an effective
area of a display portion within a unit pixel. However, since a
light shielding layer made of a metal thin film or the like in the
transistor for driving the liquid crystal display device is formed
as described above, a rate of an area of a light transmission
portion to that of the light shielding layer (opening ratio) in the
pixel reduces. Accordingly, a reduction of a transistor area by
improving a performance of the transistor or an improvement of
luminance of a backlight are necessary to develop a display device
having high luminance. However, the measure to improve the
characteristic of the transistor shows a limitation to a yield,
leading to an increase in cost. Moreover, the measure to improve
the luminance of the backlight increases an amount of energy
consumption.
From the viewpoint of the above described points, the object of the
present invention is to provide a transistor using a transparent
channel layer made of zinc oxide or the like, which is transparent
partially or entirely, because an orientation control of the zinc
oxide and a valence electron control thereof that has been
heretofore difficult is now possible. Specifically, the object of
the present invention is to provide a transistor which uses a
transparent material such as the zinc oxide or the like for a
channel layer (conductive layer) so that the channel layer does not
have a photosensitivity for the visible light region, and removes a
necessity to form a light shielding layer, thus increasing an area
rate of a display portion of a liquid crystal display device or the
like.
Furthermore, the object of the present invention is to use a
transparent transistor for various kinds of applications in an
optical device field for use in driving a light emission device
such as a plane light emission laser and an electroluminescence
device and for use in a memory. Still furthermore, the object of
the present invention is to provide a semiconductor device used as
a transparent electronic device for various kinds of wide
applications in addition to a driving circuit requiring no light
shielding layer.
According to first solving means of the present invention, a
transistor is provided,
which comprises:
a transparent channel layer using any one of zinc oxide ZnO, zinc
magnesium oxide Mg.sub.xZn.sub.1-xO, zinc cadmium oxide
Cd.sub.xZn.sub.1-xO and cadmium oxide CdO; and
a source, a drain and a gate in which a transparent conductive
material such as conductive ZnO doped or undoped with any one of
group III elements, group VII elements, group I elements and group
V elements, a transparent conductive material such as
In.sub.2O.sub.3, SnO.sub.2 and (In--Sn)O.sub.x, or an untransparent
electrode material are used partially or entirely.
According to second solving means of the present invention, a
transistor is provided,
which comprises:
an emitter and a collector, or a base which are made of a
transparent n-type semiconductor such as ZnO doped with group III
elements or group VII elements;
a base, or an emitter and a collector which are made of a
transparent p-type semiconductor such as ZnO doped with group I
element or group V elements; and
a base electrode, an emitter electrode and a collector electrode
respectively formed on the base, the emitter and the collector, in
which a transparent conductive material such as conductive ZnO
doped or undoped with any one of group III elements, group VII
elements, group I elements and group V elements, a transparent
conductive material such as InO.sub.3, SnO.sub.2 and
(In--Sn)O.sub.x, or an untransparent electrode material are used
partially or entirely.
Still another object of the present invention is to provide a
semiconductor device in which a transparent transistor is stacked,
and a semiconductor device applied to a light emission device, a
memory or the like.
BRIEF DESCRIPTIONS OF THE DRAWINGS
FIGS. 1(A) and 1(B) are section views of a first embodiment of a
transistor according to the present invention.
FIGS. 2(A) and 2(B) are section views of second and third
embodiments of a transistor according to the present invention.
FIG. 3 is a section view of a fourth embodiment of a transistor
according to the present invention.
FIG. 4 is a section view of a fifth embodiment of a transistor
according to the present invention.
FIG. 5 is a section view of a stacked type semiconductor
device.
FIGS. 6(A) and 6(B) are a section view and a circuit diagram of a
semiconductor device to which a FET according to the present
invention is applied for driving a light emission device.
FIGS. 7(A) and 7(B) are a section view and a circuit diagram of a
semiconductor device to which a bipolar transistor according to the
present invention is applied for driving a light emission
device.
FIGS. 8(A) and 8(B) are a section view and a circuit diagram of a
device to which the FET according to the present invention is
applied for controlling a memory device.
FIG. 9 is a characteristic view of a transistor of the present
invention.
PREFERABLE EMBODIMENTS OF THE INVENTION
(1) Field Effect Transistor (FET)
A section view of a first embodiment of a transistor according to
the present invention is shown in FIGS. 1(A) and 1(B). As shown in
FIG. 1(A), the transistor of the first embodiment relates to a FET,
and comprises a channel layer 11, a source 12, a drain 13, a gate
14, a gate insulating layer 15 and a substrate 16. The channel
layer 11 is formed on the substrate 16. On the channel layer 11,
formed are the gate insulating layer 15, the source 12 and the
drain 13. The gate 14 is formed on the gate insulating layer
15.
A modification of a first embodiment is shown in FIG. 1(B). In this
transistor, the channel layer 11 is formed on the substrate 16.
Furthermore, on the channel layer 11, the source 12 and the drain
13 are formed by an ohmic junction, and the gate 14 is formed
thereon by a Shottky junction. In this embodiment, since the
transistor lacks the gate insulating layer 15 unlike that of FIG.
1(A), a proper gap is provided between the gate 14 and the source
12 and between the gate 14 and the drain 13.
Materials of the respective constituent components will be
described below.
Firstly, the channel layer 11 is formed of a transparent
semiconductor. As the material of the transparent channel layer 11,
any of zinc oxide ZnO, zinc magnesium oxide Mg.sub.xZn.sub.1-xO
zinc cadmium oxide Cd.sub.xZn.sub.1-xO, cadmium oxide CdO or the
like can be used. Either a material doped with n and p-type
impurities or a material undoped with them may be used.
Secondly, a transparent electrode is used either for all of the
source 12, the drain 13 and the gate 14 or for any of them. As the
transparent electrode, a transparent conductive material such as
conductive ZnO is used, which is doped with any one of group III
elements (B, Al, Ga, In, Tl), group VII elements (F, Cl, Br, I),
group I elements (Li, Na, K, Rb, Cs) and group V elements (N, P,
As, Sb, Bi) or undoped with them. Herein, when these elements are
doped, a doping amount can be set properly. For example, though
n.sup.++-ZnO doped with n-type elements at a high concentration can
be used, elements to be doped are not limited to this. Moreover, as
the source 12, the drain 13 and the gate 14, transparent conductive
materials such as In.sub.2O.sub.3, SnO.sub.2 and (In--Sn)O.sub.x
can be used in addition to these. Besides these transparent
materials, metals such as Al and Cu and electrode materials such as
highly doped semiconductor polysilicon which is untransparent may
be used. Moreover, it is possible to adopt a transparent material
and a non-transparent material together.
Thirdly, as the gate insulating layer 15, a transparent insulating
material such as insulative ZnO doped with an element which can
take a valence of 1 as a valence number or doped with group V
element is used. As the element which can take the valence of 1,
for example, group I elements (Li, Na, K, Rb, Cs), Cu, Ag, Au or
the like are enumerated. As the group V element, N, P, As, Sb, Bi
or the like are enumerated. As the gate insulating layer 15, in
addition to these materials, a transparent insulative oxide
material such as Al.sub.2O.sub.3, MgO, CeO.sub.2, ScAlMgO.sub.4 and
SiO.sub.2 can be used. Furthermore, a transparent insulator such as
vinyl and plastic may be used. It should be noted that the gate
insulating layer 15 is preferably made of a high insulative
material offering a good lattice matching with the material of the
channel layer 11. If the channel layer 11 is made of zinc oxide,
for example, ScAlMgO.sub.4 or the like are used. These materials
are in conformity with each other in their lattice constants in all
planes thereof within 1%, and these materials can be epitaxilally
grown mutually. Moreover, by using a high dielectric material for
the gate insulating layer 15, it is also possible to allow the
transistor itself to possess a memory function. As the high
dielectric material, for example, Zn.sub.1-xLi.sub.xO,
Zn.sub.1-x(Li.sub.yMg.sub.x-y)O or the like can be used.
Fourthly, as the substrate 16, insulative materials are mainly
used. When it is intended that the substrate is made to be
transparent, for example, glass, sapphire, plastic or the like can
be used as a transparent material. Furthermore, materials that are
untransparent may be used as the substrate depending on purposes.
For example, for the purposes in which transparency is required as
a liquid crystal display screen or the like, a transparent
substrate should be used. When a zinc oxide single crystal or a
ScAlMgO.sub.4 single crystal as one of materials having the most
excellent property is used for the substrate 16, the transparent
channel layer 11, or the source 12 and the drain 13 can be grown
epitaxially on the substrate. Although some grain boundaries exist
on the substrate made of a sapphire single crystal, it is possible
to grow the channel layer 11 or the like epitaxially. Moreover, by
using the glass substrate, though an in-plane orientation is
random, it is possible to control the orientation in a thickness
direction as c-axis, and the transistor of this embodiment can show
sufficient characteristics as a driving circuit of a display
device.
In FIGS. 2(A) and 2(B), section views of second and third
embodiments of a transistor according to the present invention are
shown. The transistor of the second embodiment shown in FIG. 2(A)
relates to a FET, and comprises a channel layer 21, a source 22, a
drain 23, a gate 24, a gate insulating layer 25 and a substrate 26.
The source 22 and the drain 23 are formed on the substrate 26. The
channel layer 21 is formed so as to cover the substrate 26, the
source 22 and the drain 23. The gate insulating layer 25 is formed
on the channel layer 21. The gate 24 is formed on the gate
insulating layer 25. Herein, the gate 24, the gate insulating layer
25 and the channel layer 21 constitute a MIS structure.
A section view of the third embodiment of the transistor according
to the present invention is shown FIG. 2(B). This transistor is a
modification of the second embodiment. In the transistor shown in
FIG. 2(B), the gate insulating layer 25 is not formed unlike the
transistor shown in FIG. 2(A), and the gate 24 and the channel
layer 21 constitutes a Shottky junction structure. When the gate
insulating layer 25 is provided like the transistor shown in FIG.
2(A), a limitation to a voltage applied to the gate is small.
Contrary to this, when the gate insulating layer 25 is not provided
like the transistor shown in FIG. 2(B), withstand voltages between
the gate and the source and between the gate and the drain become
low. In this case, manufacturing processes are simplified.
A section view of a fourth embodiment of a transistor according to
the present invention is shown in FIG. 3. The transistor of the
fourth embodiment relates to a FET, and comprises a channel layer
31, a source 32, a drain 33, a gate 34, a gate insulating layer 35
and a substrate 36. The channel layer 31 is formed on the substrate
36. The gate insulating layer 35 is formed on the channel layer 31,
and the gate 34 is formed on the gate insulating layer 35. The
source 32 and the drain 33 can be formed by diffusing or
ion-implanting impurities thereinto using the gate insulating layer
35 as a mask. Moreover, as a modification of this embodiment, the
gate insulating layer 35 can be omitted by appropriately setting a
size of the gate 34 to a certain scale.
It should be noted that in the foregoing second to fourth
embodiments, materials of the constituent components are the same
as those described in the first embodiment.
(2) Bipolar Transistor
A section view of a fifth embodiment of a transistor according to
the present invention is shown in FIG. 4. The transistor of the
fifth embodiment relates to a bipolar transistor, and comprises a
base 41, an emitter 42, a collector 43, a base electrode 44, an
emitter electrode 45, a collector electrode 46 and a substrate
47.
In an npn-type transistor, the emitter 42 and the collector 43 are
formed of an n-type transparent semiconductor, and the base 41 is
formed by a p-type transparent semiconductor. The base electrode
44, the emitter electrode 45 and the collector electrode 46 are
formed respectively on the base 41, the emitter 42 and the
collector 43. Similarly, in a pnp-type transistor, the emitter 42
and the collector 43 are formed of a p-type semiconductor as shown
in parentheses, and the base 41 is formed of an n-type transparent
semiconductor. Since the bipolar transistor can allow a large
current to flow therethrough compared to the FET, the bipolar
transistor is particularly advantageous when a large current is
required for driving a laser or the like.
The materials of the constituent components will be described
below.
As the n-type transparent semiconductor, for example, n-type ZnO is
used. The n-type ZnO is ZnO doped with, for example, group III
elements (B, Al, Ga, In, TI), group VII elements (F, Cl, Br, I). As
the p-type transparent semiconductor, for example, p-type ZnO is
used. The p-type ZnO is ZnO doped with, for example, group I
elements (Li, Na, K, Rb, Cs) and group V elements (N, P, As, Sb,
Bi). A doping amount can be set to a proper value depending on a
dimension of the device, a thickness thereof, an integration degree
thereof and performance thereof.
Materials of the base electrode 44, the emitter electrode 45, and
the collector electrode 46 are the same as those of the source 12,
the drain 13 and the gate 14 described in the first embodiment.
Specifically, as the transparent electrode, a transparent
conductive material such as conductive ZnO doped with any one of
group III elements (B, Al, Ga, In, Ti), group VII elements (F, Cl,
Br, I), and group I elements (Li, Na, K, Rb, Cs) or conductive ZnO
undoped with these materials is used. Herein, when these elements
are doped, it is possible to set a doping amount to a proper value.
Although n.sup.++-ZnO or the like, which are doped with n-type
elements with a high concentration, can be used, the doping amount
is not limited to this. Moreover, as the base electrode 44, the
emitter electrode 45 and the collector electrode 46, a transparent
conductive material such as In.sub.2O.sub.3, SnO.sub.2 and
(In--Sn)O.sub.x can be used in addition to the above described
materials. Besides the transparent materials, a metal such as Al
and Cu and an untransparent electrode material such as highly doped
semiconductor polysilicon may be used. Moreover, transparent or
untransparent materials are properly selected and used for all of
the electrodes or a part of them.
(3) Stacked Type Semiconductor Device
A section view of a stacked type semiconductor device is shown in
FIG. 5. FIG. 5 shows, as an example, a case where the transistors
of the first embodiment are stacked. Specifically, a second
transistor is further formed on a transistor which comprises a
channel layer 11, a source 12, a drain 13, a gate 14, a gate
insulating layer 15 and a substrate 16. At this time, an insulating
layer 57 and a conductive shielding layer 58 are formed between the
first and second transistors. The conductive shielding layer 58
serves to electrically shield the first and second transistors from
one another. As the second transistor, an insulating layer 59
serving as a substrate is formed, and a second source 52 and a
second drain 53 are formed thereon. Moreover, a second channel
layer 51 is formed so as to cover the insulating layer 59, the
second source 52 and the second drain 53, and a second gate
insulating layer 55 and a second gate 54 are formed thereon.
Materials of the insulating layers 57 and 59 may be the same as
that of the gate insulating layer 15, and another insulating
material identical to that of the transparent substrate 16 may be
used. As a material of the conductive shielding layer 58, the same
material as that of the source 12, the drain 13 and the gate 14 can
be used. By forming the insulating layer 57 or 59 so as to have a
thickness larger than that of either the channel layer 11 or the
channel layer 11 and the gate insulating layer 15, the conductive
shielding layer 58 and the insulating layer 57 or 59 can be
omitted.
When the transistors are stacked upon another, the channel layer
11, the second channel layer 51 or the insulating layer 57 is
preferably flattened suitably according to demand. Note that since
there is a possibility of increasing cost by adding flattening
processes, any of these layers may be flattened properly.
Furthermore, as to the number of the stacked transistors, the
suitable number of the transistors can be stacked according to
demand. Furthermore, the transistors of the foregoing first to
fifth embodiments are suitably selected and can be stacked. Still
furthermore, the plural kinds of transistors may be selected to be
stacked mixedly upon another.
(4) Application to Light Emission Device
A section view and a circuit diagram of a semiconductor device to
which the FET according to the present invention is applied for
driving a light emission device are shown in FIGS. 6(A) and 6(B).
Reference symbols a, b and c in the section view of FIG. 6(A)
correspond to reference symbols a, b and c in the circuit diagram
of FIG. 6(B). In this device, a transistor is formed of a channel
layer 61, a source 62, a drain 63, a gate 64, a gate insulating
layer 65 and a substrate 66. A semiconductor layer 67 is formed on
the region of the drain 63, whereby the drain 63 and the
semiconductor layer 67 form a light emission portion. Moreover, a
source electrode 68, a gate electrode 69 and a light emission
portion electrode 60 are provided in this device. As to the light
emission portion, when an n-type semiconductor is used for the
drain 63, a p-type semiconductor is used for the semiconductor
layer 67. On the other hand, when a p-type semiconductor is used
for the drain 63, an n-type semiconductor is used for the
semiconductor layer 67.
A transparent semiconductor material identical to that of the gate
64 is used for the semiconductor layer 67, and a transparent
electrode material is used for the light emission portion electrode
60. Thus, the light emission portion of this device is enabled to
perform a plane light emission in the upward direction in FIG.
6(A). Furthermore, by using a transparent material for the
substrate 66, the light emission portion thereof is enables to
perform the plane light emission in the downward direction in FIG.
6(A). In addition, if a light emission zone is equal to an
ultraviolet zone, a light emitted from the light emission portion
can be converted into a visible light by disposing fluorescent
substance either on the light emission portion or under the light
emission portion, in other words, on the semiconductor layer 67 and
the light emission portion electrode 60 or under the substrate
66.
A section view and a circuit diagram of a semiconductor device to
which the bipolar transistor according to the present invention is
applied for driving a light emission device are shown in FIGS. 7(A)
and 7(B). Reference symbols a, b and c in the section view of FIG.
7(A) correspond to reference symbols a, b and c in the circuit
diagram of FIG. 7(B). In this device, a transistor is formed of a
base 71, an emitter 72, a collector 73, a base electrode 74, a
collector electrode 76 and a base 77. Furthermore, a semiconductor
layer 78 is formed on a region of the emitter 72, whereby the
emitter 72 and the semiconductor layer 78 form a light emission
portion. In addition, a light emission portion electrode 79 is
formed on the semiconductor layer 78. When an n-type semiconductor
is used as the emitter 72, a p-type semiconductor is used for the
semiconductor layer 78. On the other hand, when a p-type
semiconductor is used as the emitter 72, an n-type semiconductor is
used for the semiconductor layer 78.
The light emission portion is enabled to perform a plane light
emission in the upward direction in FIG. 7(A) by using a
transparent semiconductor material identical to that of the base 71
for the semiconductor layer 78 and a transparent electrode material
for the light emission portion electrode 79. Moreover, by using a
transparent material for the substrate 77, the light emission
portion is enabled to perform a plane light emission in the
downward direction in FIG. 7(A). If a light emission zone is equal
to an ultraviolet zone, a light emitted from the light emission
portion can be converted into a visible light by disposing a
fluorescent substrate on the light emission portion or under the
light emission portion, in other words, on the semiconductor layer
78 and the light emission portion electrode 79 or under the
substrate 77.
It should be noted that the transistors of the first to third
embodiments can be combined with each other for use in driving by
forming a light emission portion. Moreover, in the foregoing
descriptions, a region continuous with the source or the drain (the
collector or the emitter) is used in a part of the light emission
portion. In addition to this, a different semiconductor region
continuous with the source or the drain (the collector or the
emitter) is formed, and this region may be used as a part of the
light emission portion. Moreover, the light emission portion may be
a light-emitting diode or a laser diode, and a proper light
emission device can be formed. Moreover, when the present invention
is applied, a semiconductor device, which is entirely transparent,
can be fabricated by driving a transparent ZnO light emission
device by the use of the transparent transistor. The light emission
device can also be made to be partially transparent.
As the light emission portion, proper structures such as a
multilayered reflection film, a double hetero structure and a plane
light emission structure are adopted, and they can be combined with
each other. Moreover, a plurality of the light emission portions
and the transistors are arranged in a matrix fashion, and each of
the light emission portions is driven by the transparent
transistor, whereby the light emission portion can be applied to a
display, an illumination panel, a partial light adjusting panel or
the like suitably.
(5) Application to Memory
A section view and a circuit diagram of a device in which the FET
according to the present invention is applied to a control of a
memory device are shown in FIGS. 8(A) and 8(B). Reference symbols
a, b and c of FIG. 8(A) correspond to reference symbols a, b and c
of FIG. 8(B). In this device, a transistor is formed of a channel
layer 81, a source 82, a drain 83, a gate 84, a gate insulating
layer 85 and a substrate 86. On the source 82, formed is a
conductive layer 88 made of a transparent conductive material
identical to that of the source 82. Furthermore, on a region of the
drain 83, formed is a semiconductor layer or a conductive layer 87
with the gate insulating layer 85 interposed therebetween, and thus
these constituent components form a capacitor. Herein, though the
gate insulating layer 85 is used as an inter-electrode insulator of
the capacitor, a different insulating layer from this gate
insulating layer 85 may be formed to be used. Furthermore, as an
electrode of the capacitor, a region continuous to the source or
the drain may be used, or alternatively another semiconductor
region or another conductive region, which is connected to the
source or the drain, may be used. An electrode material forming the
capacitor may be a transparent material or an untransparent
material, and the transparent material may be partially used for
the electrode material of the capacitor. By properly using the
transparent material for these layers and these regions, it is
possible to fabricate a memory device which is entirely transparent
or partially transparent.
Also when the bipolar transistor according to the present invention
is used, the application to the memory device is possible by
forming a capacitor on the substrate properly. Specifically, for
example, in the bipolar transistor as in the foregoing embodiments,
a capacitor can be formed of a region continuous to the collector
or the emitter or a region of another semiconductor or another
conductor connected to the collector or the emitter, the insulating
layer on this region, and the semiconductor layer or the conductive
layer on the insulating layer.
When the bipolar transistor is applied to the memory device, the
memory device can be realized by arranging the transistors and the
capacitors in a matrix fashion and by driving the capacitors by the
corresponding transistors.
(6) Characteristics
An example of the characteristic view of the transistor according
to the present invention is shown in FIG. 9. FIG. 9 shows an
example of a change in a drain current (axis of ordinates) with
regard to the FET using ZnO for the channel layer when a drain
current (axis of abscissa) is changed in the first embodiment of
the present invention. Herein, a thickness of the ZnO channel layer
was set to 200 nm, a thickness of the gate insulating layer was set
to 100 nm, a gate length was set to 600 .mu.m, and a gate width was
set to 200 .mu.m. A gate voltage V.sub.G was set to 0 V and a range
from -0V to -8V.
(7) Other Applications
The transistor of the present invention can be fabricated on the
same substrate together with the light emission device, the
capacitor and other devices. Moreover, the same kind of transistor
or different kinds of transistors of the present invention are
formed, and transparent materials can be used for wiring between
the transistors. The transistors and the devices driven by these
transistors can be formed so as to be entirely or partially
transparent properly. Moreover, a size, a thickness and a dimension
of the transistor can be properly set in accordance with purposes,
processes or the like. A doping amount can be properly set in
accordance with manufacturing processes, device performance or the
like according to demand.
Furthermore, as a transparent n-type semiconductor, a transparent
n-type semiconductor, a transparent conductive material and a
transparent insulating material, the example in which elements are
doped on the basis of the ZnO semiconductor was described. However,
the present invention is not limited to this. For example, besides
zinc oxide ZnO, elements may be doped on the basis of a transparent
material such as zinc magnesium oxide Mg.sub.xZn.sub.1-xO, zinc
cadmium oxide Cd.sub.xZn.sub.1-xO, cadmium oxide CdO or the like
properly.
Besides the foregoing ways, it is possible to realize a
semiconductor device which is entirely or partially transparent by
applying to a transistor performing signal processing by driving a
detector for detecting light ranging from ultraviolet zone to X-ray
zone, to an oxygen sensor, and to a device obtained by combining a
sound wave, Surface Acoustic Wave (SAW) or piezoelectric property.
Moreover, the present invention enables an electronic circuit to
attach on a window glass of a car, a house or the like, a
transparent plastic board or the like. The present invention can
manufacture computer peripheral equipment for example, a keyboard,
a touch panel and a pointing device so as to be transparent. By
being transparent, they can be manufactured confidentially, or they
can be manufactured so as to be hard to look from some other place.
Moreover, it is possible to propose something original in terms of
design. In addition to these, an application range of the present
invention is very wide.
INDUSTRIAL APPLICABILITY
The present invention can provide the transistor using the
transparent channel layer made of zinc oxide or the like, which is
entirely or partially transparent. Specifically, according to the
present invention, by using the transparent material such as zinc
oxide or the like for the channel layer (conductive layer), the
transistor can be provided, which offers no light sensitivity
within the visible light region, thus removing a necessity to form
the light shielding layer, and increases the area rate of the
display portion of the liquid crystal display device or the
like.
Furthermore, according to the present invention, the transparent
transistor can be used for various kinds of applications in an
optical device field for use in driving a light emission device
such as a plane light emission laser and an electroluminescence
device and for use in a memory. Still furthermore, according to the
present invention, the semiconductor device can be provided, which
is used as a transparent electronic device for various kinds of
wide applications in addition to a driving circuit requiring no
light shielding layer.
* * * * *